Gastrointestinal nematodes can affect sheep productivity due severe weight loss, anemia and sequential dead that cause in animals with high level of infection. Infection control is generally performed with synthetics anthelmintic; however, the indiscriminate use of these drugs culminates in the emergence of resistant nematodes. Thus, alternatives to the use of synthetic anthelmintic have been proposed, such as the inclusion of medicinal plants in animal feed. In this context, the objective of the study was evaluate the anthelmintic activity of the leaves of medicinal plant Psidium cattleianum Sabine (araçá) through of its hydroalcoholic extract using in vitro assays with eggs and larvae of nematodes obtained from naturally infected donor sheep. The extract showed good in vitro ovicidal and larvicidal activity with IC50 values of 0.55 mg/mL for egg hatching inhibition, 0.20 mg/mL for larval development inhibition and efficiency greater than 80% in inhibition of larval migration in all concentrations evaluated (IC50 < 0.19 mg/mL). Phytochemical analysis detected higher concentrations saponins, flavonoids, cardiac glycosides, anthraquinones, and tannins in the extract. Our results demonstrated that the Psidium cattleianum Sabine leaves exhibits in vitro anthelmintic activity, suggesting that, beyond its other medicinal properties, this plant can also be an ally for gastrointestinal nematodes control in sheep.